1. Field of the Invention
The present invention relates to managing power in an electronic system having a plurality of electronic devices.
2. Description of the Related Art
Servers and other computer hardware are often grouped together on a rack to conserve space and place the servers and infrastructure in a central location for access by an administrator. Managing these “rack systems” can be easier and less expensive than separately administering a multitude of scattered servers. Rack systems are available in a range of size, density, and design. Some rack systems may be built around servers that are self-supporting in that each server has an individual chassis, on-board power supply, cooling fan, and other support devices. The self-supporting servers may be grouped in a rack or tower configuration and networked to each other and to client computers. A higher density rack system can be achieved using leaner “blade servers” with shared support modules that are connected in a multi-blade chassis. Blade servers generally achieve greater density due to having a narrower form factor and sharing support modules such as blower and power modules. Some of the more compact rack system server arrangements presently available include the SYSTEM X servers and eServer BLADECENTER available from IBM (IBM, BLADECENTER, and SYSTEM X are registered trademarks of International Business Machines Corporation, Armonk, N.Y.).
Power management is important for many aspects of operating a rack system, such as to minimize the costs of operating the servers, minimize the heat generated by the servers, and to optimize the performance and efficiency of the system. Increasingly, server power is being monitored and limited by power capping according to a user-settable power limit (interchangeably referred to as a “power cap”). A feedback-based power management system may be used to “throttle” the processors and/or memory on a server to enforce the power limit. For example, some servers include a Baseboard Management Controller (BMC) that a service processor may use to monitor real-time power consumption by a server and throttle the processors as necessary to enforce the power limit. The processors are throttled down to sacrifice performance for the sake of enforcing the power limit. In cases where the power limit was chosen due to a physical power distribution limitation of the associated datacenter, the power capping feature prevents excessive stress on the power distribution pathways. In other cases, the user may choose to limit power for budgetary reasons, in which case power capping helps control the cost of running a datacenter. Power-capping is used to limit power consumption even though the datacenter infrastructure may be able to support additional power demands.
Whether for a single computing device (e.g. a server) or a network of multiple devices (e.g. a rack of networked servers), computing power consumption is generally dynamic, rather than constant. Because power demand varies with time, there will typically be some periods during which power demanded by the datacenter or subsystems thereof exceeds a specified power limit, and other times when power demand is less than the specified power limit. When demand exceeds a threshold, power consumption is limited by power capping. However, when demand is less than the threshold, the datacenter or subsystems thereof may be underutilized. It would therefore be desirable to develop a power management solution that compensates for the periods of underutilization, to maximize server throughput.